Chemistry MCQ with Answer and Explanation : Oxidation and Reduction.

Here below some basic MCQ’s about “Oxidation and Reduction” with answer which is explained in details. Let’s check one by one.

Question 1:

Which of the following processes represents oxidation?
A) Fe2+→Fe3++e−Fe2+→Fe3++e−
B) Cu2++2e−→CuCu2++2e−→Cu
C) O2+4e−+4H+→2H2OO2​+4e−+4H+→2H2​O
D) H2→2H++2e−H2​→2H++2e−

Answer: A) Fe2+→Fe3++e−Fe2+→Fe3++e−

Explanation: Oxidation is defined as the loss of electrons. In option A, iron (II) loses an electron to become iron (III).

---

Question 2:

In the reaction 2H2+O2→2H2O2H2​+O2​→2H2​O, which substance is reduced?
A) H2H2​
B) O2O2​
C) H2OH2​O
D) None of the above

Answer: B) O2O2​

Explanation: Reduction is the gain of electrons. Oxygen in this reaction gains electrons (it goes from 0 in O2O2​ to -2 in H2OH2​O).

---

Question 3:

Identify the reducing agent in the reaction 2Na+Cl2→2NaCl2Na+Cl2​→2NaCl.
A) NaNa
B) Cl2Cl2​
C) NaClNaCl
D) None of the above

Answer: A) NaNa

Explanation: The reducing agent is the substance that donates electrons and is oxidized in the process. Sodium is oxidized from 0 to +1.

---

Question 4:

Which of the following statements is true regarding oxidation and reduction?
A) Oxidation involves gain of electrons.
B) Reduction involves loss of electrons.
C) Oxidation and reduction can occur simultaneously.
D) None of the above.

Answer: C) Oxidation and reduction can occur simultaneously.

Explanation: Oxidation and reduction always occur together in a redox reaction; when one substance is oxidized, another must be reduced.

---

Question 5:

In which of the following reactions is sulfur being oxidized?
A) S+O2→SO2S+O2​→SO2​
B) SO2+H2O→H2SO4SO2​+H2​O→H2​SO4
C) H2S→S+H2H2​S→S+H2​
D) 2S+3O2→2SO32S+3O2​→2SO3

Answer: D) 2S+3O2→2SO32S+3O2​→2SO3

Explanation: In this reaction, sulfur goes from 0 in elemental form to +6 in SO3SO3​, indicating it is being oxidized.

Question 6:

What is the oxidation state of sulfur in H2SO4H2​SO4​?
A) +4
B) +6
C) -2
D) 0

Answer: B) +6

Explanation: In H2SO4H2​SO4​, the oxidation state of sulfur is +6, calculated as follows: 2(+1)+x+4(−2)=02(+1)+x+4(−2)=0 leads to x=+6x=+6.

---

Question 7:

Which of the following is a characteristic of a reducing agent?
A) It is oxidized in the reaction.
B) It gains electrons.
C) It is reduced in the reaction.
D) None of the above.

Answer: A) It is oxidized in the reaction.

Explanation: A reducing agent donates electrons and, in doing so, becomes oxidized itself.

---

Question 8:

In the reaction Zn+Cu2+→Zn2++CuZn+Cu2+→Zn2++Cu, what is oxidized?
A) ZnZn
B) Cu2+Cu2+
C) Zn2+Zn2+
D) CuCu

Answer: A) ZnZn

Explanation: Zinc is oxidized as it loses electrons to become Zn2+Zn2+.

---

Question 9:

What is the product of the reduction of MnO4−MnO4−​ in an acidic solution?
A) MnO2MnO2​
B) Mn2+Mn2+
C) Mn2O7Mn2​O7​
D) MnO42−MnO42−​

Answer: B) Mn2+Mn2+

Explanation: In acidic conditions, permanganate ions MnO4−MnO4−​ are reduced to Mn2+Mn2+.

---

Question 10:

Which of the following represents a redox reaction?
A) H2+Cl2→2HClH2​+Cl2​→2HCl
B) 2Na+2H2O→2NaOH+H22Na+2H2​O→2NaOH+H2​
C) CaCO3→CaO+CO2CaCO3​→CaO+CO2​
D) NaCl→Na+Cl2NaCl→Na+Cl2​

Answer: B) 2Na+2H2O→2NaOH+H22Na+2H2​O→2NaOH+H2​

Explanation: In this reaction, sodium is oxidized (loses electrons) and water is reduced (gains electrons).